# CVE-2026-39376: FastFeedParser has an infinite redirect loop DoS via meta-refresh chain

> An attacker can cause a denial of service in FastFeedParser by triggering an infinite recursion loop via chained meta-refresh redirects.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Apr 2026
- **Updated:** 8 Apr 2026
- **Also known as:** GHSA-4gx2-pc4f-wq37, PYSEC-2026-60

## What is CVE-2026-39376?

CVE-2026-39376 is a high-severity denial of service vulnerability in kagisearch fastfeedparser, published on 7 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

FastFeedParser is a high performance RSS, Atom and RDF parser. Prior to 0.5.10, when parse() fetches a URL that returns an HTML page containing a <meta http-equiv="refresh"> tag, it recursively calls itself with the redirect URL — with no depth limit, no visited-URL deduplication, and no redirect count cap. An attacker-controlled server that returns an infinite chain of HTML meta-refresh responses causes unbounded recursion, exhausting the Python call stack and crashing the process. This vulnerability can also be chained with the companion SSRF issue to reach internal network targets after bypassing the initial URL check. This vulnerability is fixed in 0.5.10.

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2026-39376?

3 open source packages ship an affected version, including fastfeedparser. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `fastfeedparser` | PyPI | All versions | 0.5.10 |
| `fastfeedparser` | PyPI | All versions | 0.5.10 |
| `fastfeedparser` | PyPI | All versions | 0.5.10 |

Products: Kagi Fastfeedparser.

## How do I fix CVE-2026-39376?

Upgrade fastfeedparser to 0.5.10 or later.

## Is CVE-2026-39376 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39376 exists.

Public exploit code:

- CVE-2026-39376(Infinite redirect loop DoS via meta-refresh chain) (github_poc): https://github.com/redyank/CVE-2026-39376

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39376 and fix it if it is affected.

What it is: CVE-2026-39376 is a high-severity denial of service vulnerability in kagisearch fastfeedparser, published on 7 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39376 exists.

Affected packages and fixed versions:
- fastfeedparser (PyPI): affected all versions; fixed in 0.5.10
- fastfeedparser (PyPI): affected all versions; fixed in 0.5.10
- fastfeedparser (PyPI): affected all versions; fixed in 0.5.10

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-39376/ (Markdown: https://insights.sbomify.com/CVE-2026-39376/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39376
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39376
- OSV: https://osv.dev/vulnerability/CVE-2026-39376

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39376/
Summaries are generated and may contain mistakes; the official description above is the record.